<?php

namespace PhpZip\Crypto;

use PhpZip\Exception\ZipAuthenticationException;
use PhpZip\Exception\ZipCryptoException;
use PhpZip\Model\ZipEntry;
use PhpZip\Util\CryptoUtil;
use PhpZip\Util\PackUtil;

/**
 * Traditional PKWARE Encryption Engine.
 *
 * @see https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT .ZIP File Format Specification
 * @author Ne-Lexa alexey@nelexa.ru
 * @license MIT
 */
class TraditionalPkwareEncryptionEngine implements ZipEncryptionEngine
{
    /**
     * Encryption header size
     */
    const STD_DEC_HDR_SIZE = 12;

    /**
     * Crc table
     *
     * @var array
     */
    private static $CRC_TABLE = [
        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
        0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
        0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
        0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
        0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
        0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
        0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
        0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
        0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
        0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
        0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
        0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
        0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
        0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
        0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
        0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
        0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
        0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
        0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
        0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
        0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
        0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
        0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
        0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
        0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
    ];

    /**
     * Encryption keys
     *
     * @var array
     */
    private $keys = [];
    /**
     * @var ZipEntry
     */
    private $entry;

    /**
     * ZipCryptoEngine constructor.
     *
     * @param ZipEntry $entry
     */
    public function __construct(ZipEntry $entry)
    {
        $this->entry = $entry;
    }

    /**
     * Initial keys
     *
     * @param string $password
     */
    private function initKeys($password)
    {
        $this->keys[0] = 305419896;
        $this->keys[1] = 591751049;
        $this->keys[2] = 878082192;
        foreach (unpack('C*', $password) as $b) {
            $this->updateKeys($b);
        }
    }

    /**
     * Update keys.
     *
     * @param string $charAt
     */
    private function updateKeys($charAt)
    {
        $this->keys[0] = self::crc32($this->keys[0], $charAt);
        $this->keys[1] = $this->keys[1] + ($this->keys[0] & 0xff);
        $this->keys[1] = PackUtil::toSignedInt32($this->keys[1] * 134775813 + 1);
        $this->keys[2] = PackUtil::toSignedInt32(self::crc32($this->keys[2], ($this->keys[1] >> 24) & 0xff));
    }

    /**
     * Update crc.
     *
     * @param int $oldCrc
     * @param string $charAt
     * @return int
     */
    private function crc32($oldCrc, $charAt)
    {
        return (($oldCrc >> 8) & 0xffffff) ^ self::$CRC_TABLE[($oldCrc ^ $charAt) & 0xff];
    }

    /**
     * @param string $content
     * @return string
     * @throws ZipAuthenticationException
     */
    public function decrypt($content)
    {
        $password = $this->entry->getPassword();
        $this->initKeys($password);

        $headerBytes = array_values(unpack('C*', substr($content, 0, self::STD_DEC_HDR_SIZE)));
        $byte = 0;
        foreach ($headerBytes as &$byte) {
            $byte = ($byte ^ $this->decryptByte()) & 0xff;
            $this->updateKeys($byte);
        }

        if ($this->entry->getGeneralPurposeBitFlag(ZipEntry::GPBF_DATA_DESCRIPTOR)) {
            // compare against the file type from extended local headers
            $checkByte = ($this->entry->getDosTime() >> 8) & 0xff;
        } else {
            // compare against the CRC otherwise
            $checkByte = ($this->entry->getCrc() >> 24) & 0xff;
        }
        if ($byte !== $checkByte) {
            throw new ZipAuthenticationException("Bad password for entry " . $this->entry->getName());
        }

        $outputContent = "";
        foreach (unpack('C*', substr($content, self::STD_DEC_HDR_SIZE)) as $val) {
            $val = ($val ^ $this->decryptByte()) & 0xff;
            $this->updateKeys($val);
            $outputContent .= pack('c', $val);
        }
        return $outputContent;
    }

    /**
     * Decrypt byte.
     *
     * @return int
     */
    private function decryptByte()
    {
        $temp = $this->keys[2] | 2;
        return (($temp * ($temp ^ 1)) >> 8) & 0xffffff;
    }

    /**
     * Encryption data
     *
     * @param string $data
     * @return string
     */
    public function encrypt($data)
    {
        $crc = $this->entry->isDataDescriptorRequired() ?
            ($this->entry->getDosTime() & 0x0000ffff) << 16 :
            $this->entry->getCrc();
        $headerBytes = CryptoUtil::randomBytes(self::STD_DEC_HDR_SIZE);

        // Initialize again since the generated bytes were encrypted.
        $password = $this->entry->getPassword();
        $this->initKeys($password);

        $headerBytes[self::STD_DEC_HDR_SIZE - 1] = pack('c', ($crc >> 24) & 0xff);
        $headerBytes[self::STD_DEC_HDR_SIZE - 2] = pack('c', ($crc >> 16) & 0xff);

        $headerBytes = $this->encryptData($headerBytes);
        return $headerBytes . $this->encryptData($data);
    }

    /**
     * @param string $content
     * @return string
     * @throws ZipCryptoException
     */
    private function encryptData($content)
    {
        if (null === $content) {
            throw new ZipCryptoException('content is null');
        }
        $buff = '';
        foreach (unpack('C*', $content) as $val) {
            $buff .= pack('c', $this->encryptByte($val));
        }
        return $buff;
    }

    /**
     * @param int $byte
     * @return int
     */
    private function encryptByte($byte)
    {
        $tempVal = $byte ^ $this->decryptByte() & 0xff;
        $this->updateKeys($byte);
        return $tempVal;
    }
}
